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RF Designer - Components (Ideal Transmission Line Elements)

Posted: Wed Jan 07, 2015 4:45 am
by rftools
Ideal Transmission Line Elements

TLIN - Ideal Transmission Line

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NameDescriptionUnitsDefault Value
ZImpedanceResistance50 ohms
ELElectrical lengthDegrees90º
F0Frequency where EL is specifiedFrequency1000 MHz


Model for an ideal and lossless transmission line. Electrical length (EL) is specified in degrees or radians at frequency F0.

TLOC - Ideal Open Circuited Transmission Line

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NameDescriptionUnitsDefault Value
ZImpedanceResistance50 ohms
ELElectrical lengthDegrees45º
F0Frequency where EL is specifiedFrequency1000 MHz


Model for an ideal and lossless open circuited transmission line. Electrical length (EL) is specified in degrees or radians at frequency F0.

TLSC - Ideal Short Circuited Transmission Line

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NameDescriptionUnitsDefault Value
ZImpedanceResistance50 ohms
ELElectrical lengthDegrees45º
F0Frequency where EL is specifiedFrequency1000 MHz


Model for an ideal and lossless short circuited transmission line. Electrical length (EL) is specified in degrees or radians at frequency F0.

TLIN4 - Ideal 4 Node Transmission Line

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NameDescriptionUnitsDefault Value
ZImpedanceResistance50 ohms
ELElectrical lengthDegrees90º
F0Frequency where EL is specifiedFrequency1000 MHz


Model for an ideal and lossless transmission line with the ground terminals left open and available as ports in the schematic. Electrical length (EL) is specified in degrees or radians at frequency F0.

CLIN - Ideal Coupled Transmission Line

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NameDescriptionUnitsDefault Value
ZoeEven-mode impedanceResistance69 ohms
ZooOdd-mode impedanceResistance36 ohms
ELElectrical lengthDegrees90º
F0Frequency where EL is specifiedFrequency1000 MHz


Model for a pair of lossless symmetric coupled transmission lines. Electrical length is specified in degrees or radians at frequency F0. Coupling is determined by the even and odd mode impedances (Zoe and Zoo).
Given a desired coupling C in decibels, Zoe = Zo * sqrt((1 + k) / (1 - k)) where k = power(10.0, -C/20.0). Zoo can the be found by solving Zoo = Zo * sqrt((1 - k) / (1 + k))

Example: Find Zoe and Zoo for a 10 dB coupler in a 50 ohm system.
First calculate k as k = power(10.0, -10/20) = 0.316
Zoe is found as Zoe = Zo * sqrt((1 + .316) / (1 - .316)) = 69.4 ohms
Zoo is found as Zoo = Zo * sqrt((1 - .316) / (1 + .316)) = 36 ohms